This invention relates to a sight mount for a firearm having the capability of use with a plurality of interchangeable sighting devices.
The precision marksman has come to recognize that variations in range, lighting and weather conditions call for the use of different sights in order to maintain a high degree of accuracy. At a minimum, the dedicated marksman utilizes a day scope and a night scope. As firing conditions demand, the sight is changed requiring a mechanical disassembly of the sight and the sight mount followed by a reassembly and attachment of the replacement sight. In order to achieve accuracy, the newly mounted sighting device is subjected to a number of adjustments. These may include not only a resighting of the device but also a repositioning of the sight support on the firearm to achieve the desired spacing between the sight and the eye of the marksman. Further, the problem of sight misalignment occurs not only from activity at the time of changing sights but also during normal use as a result of insecure sight mounts.
A wide number of different sight mounts have been used with varying results. For example, the use of scope rings which surround the firearm barrel and the generally cylindrical telescopic sight have been used. In U.S. Pat. No. 4,835,895 to Bowen, a ring system for mounting on a barrel using spaced rings is shown. The use of spaced supports renders the device susceptible to misalignment if the sight is to be replaced in the rings. Replacement of the rings requires resighting. Furthermore, barrel mounts result in long eye relief since the sighting device is mounted well away from the aiming eye.
One alternative to the use of spaced rings is seen in U.S. Pat. No. 4,845,871 wherein a fixed base is attached to the firearm and a slidable support is held in position by use of cam locks. The use of cam surfaces in precision sighting is not favored due to the sensitivity of the device. At the long distances involved, any slight variations in alignment are greatly magnified in the target area. A second alternative to the barrel mounted ring approach is shown in U.S. Pat. No. 4,021,954 to Crawford wherein the sight mount utilizes a single clamping device which surrounds the barrel. Guideways are provided in the clamping device for receiving an intermediate adapter. The sight or scope is positioned in the adapter and held by clamping bolts. The adapter can be released from a fixed position. This permits axial adjustment and enables the sight to be replaced by the steps of releasing the clamping bolts, performing the replacement or adjustment and then retightening the assembly. There are several distinct operations performed with clamping devices, each of which has the potential to alter the accuracy of the sight. In summary, the device is cumbersome and requires several steps to change the eye relief for the scope.
For the most part, mounts for sighting devices are designed for use with particular types or models of firearms. As a result, a large number of sight mounts exist to accommodate the different fixed sighting devices and the need to locate the mounting device so that it does not interfere with the ejection of cartridges. In U.S. Pat. No. 4,941,277 to Lawlor, a sight mount for attachment to the fixed rib on a barrel is disclosed. The device utilizes a plurality of clamping bolts to urge the open ends of an extrusion into engagement with the rib. The top of the extrusion is provided with a guideway dimensioned to fit the guideway of a particular scope. The device disclosed appears limited in its application to a particular sight geometry.
The importance of providing for the use of multiple scopes in a single mount is recognized in the two sight mount shown in U.S. Pat. No. 5,134,798. This device establishes a difference in elevation between sight positions to permit mounting of two scopes on a single mount. The eye relief for the two scopes is fixed at different distances which is a distinct disadvantage to the marksman.
Accordingly, the present invention is directed to the provision of mounting device having ease of interchangeability to permit use of replacement scopes without disassembling of the device. Furthermore, the eye relief between scope and the aiming eye can be readily adjusted in the subject invention without requiring the use of tools. In addition, the invention secures the scope or sighting device to the mount with a single securing element and facilitates interchangeability of sights without requiring resighting or other mechanical adjustment. The use of a single securing element essentially eliminates misalignment due to torsional or other forces applied to the mount during normal use.